TheImprovement ofTropical and Subtropical Rangelands

280 IMPROVEMENT OF TROPIOAL AND SUBTROPIOAL RANGELANDS
by nomads (which are larger and more productive than those raised
by the peasants) seem to be an equally important factor in initiating
movement. The nomads' sheep are neither as resistant to cold as
those of the northern mountain peasants nor are they as resistant
to heat as those of the lowland peasants. Huge losses are common
among the herds of tribesmen forced to settle for a full year in one
place. This abnormally high rate of attrition would seem to indicate
that the sheep raised by nomads are genetically adjusted to the utilization
of pastures at varying altitudes in different times of the year
in order to avoid climatic extremes. If 80, migration is essential to
the continued health and productivity of the sheep upon which the
viability of the Basseri economy depends.o
During the winter months, the Basseri are widely dispersed in
the low hill country near the Persian Gulf south of Jahrom and west
of Lar. Although the higher valleys and mountain slopes to the north
are covered by a blanket of snow, these southern hills are free from
snowfall. Although winters are cool, they are not unbearable, and
the occurence of cyclonic storms from the Mediterranean region is
frequent enough to make the region fairly well-watered. The grass
cover is sufficient to permit good grazing as long as the rains are
plentiful, and the characteristic settlement pattern at this time of
year is one of extreme dispersal. Families are scattered, singly or
in very small herding units of two to five tents, on higher ground
between the seasonal streams to avoid floods and wet lowlands.
March sees the beginning of movement towards the summer pastures.
Pastures begin to dry up first in the lowlands, while pasturage
in the middle altitudes is still quite good. Thus, in March the Basseri
begin to move off the hills into the uncultivated valleys in the lowland
area and congregate in the Benorou-Mansurabad plain. By the
end of the Persian New Year celebrations (the spring equinox), this
concentration is completed. All the nomads then move northward
in succession, in camps of 10 to 40 tents, over a series of mountains
and valleys past Jahrom, heading always towards the still-productive
pastures of the north. By the end of June or the beginning of May,
the Basseri reach the Mary Dasht plain. Here a bottleneck is apt to
develop, since other tribes with large herds are passing through the
area at the same time.
After crossing the Rud-e Bur by the Plu-e Kaha or Band-e Amir
bridges or by ferries, the Basseri split into a number of groups to
make the best possible use of the available pastures. In the last
stage of the migration, the Basseri go as far as the upper reaches of